Methods and arrangements to construct trailers for boats are previously known in a number of different embodiments.
As an example of the background of the invention and the technical field to which the invention relates, it may be mentioned that, at least by public practice, previously a trailer adapted for a boat is known, having a chassis shaped like a “U”, provided with wheels and having a number of vertically adjustable struts supported by the chassis and one or more carrying slings or the like oriented between struts coordinated in pairs, which slings are intended to let said boat be supported hanging in the same carrying slings by directly or indirectly abutting against an outer surface of a hull belonging to the boat.
Said chassis is formed by two flexurally rigid branches, each one being turnably related and connected with a connecting part of a first end portion of the respective branch and where at least one strut, out of a selected number of struts, consists of a hydraulically operating piston-cylinder arrangement, having the cylinder part facing towards and attached to the chassis and the piston part arranged movable up and down by means of a hydraulic oil supplied or drawn off via valve arrangements designed for this.
A trailer, of this category, has piston-cylinder arrangements coordinated in pairs, one pair for the stem of the boat, one or two pairs for the stern of the boat, and which are vertically adjustable in synchronism, in order to keep the hull of the boat hanging in carrying slings.
One or both of the astern carrying slings will come to carry the main part of the weight of the boat, with a larger friction effect activable between the carrying slings and the astern portion of the hull of the boat, while the forward carrying sling will come to carry a considerably lesser part of the weight of the boat, with a considerably lesser friction effect activable between the carrying sling and the forward portion of the hull of the boat.
This implies that a rocking or rolling of the hull of the boat, about a longitudinal axis assigned to the hull of the boat, caused primarily by a twisting of one branch relative the other branch in relation to the connecting part, will, by virtue of the lesser friction effect, create a relative motion between the forward carrying sling and the forward portion of the hull of the boat, a relative motion that normally may inflict larger or smaller damages to the forward portion of the hull of the boat as well as normally may inflict wear of the carrying sling.